Computer coordinate input devices, commonly called digitizers, are known in the art and designed to determine the coordinates of a point specified by an operator by way of a pointing device, such as a stylus. The user manipulates the stylus over the digitizer tablet within its sensing proximity, with the tablet picking up stylus frequency signals so as to locate the stylus position and switch state. Generally, the information received by the digitizer tablet is processed in accordance with a program, namely, tablet driver software commonly termed the tablet driver which is typically provided by the tablet and stylus manufacturer and installed in the computer. The processed information is then transferred to the operating system (OS) or application program of the computer for subsequent viewing on the display screen.
Such known digitizer coordinate input systems are disclosed for example in commonly owned U.S. Pat. Nos. 4,878,553 and 4,848,496.
Additionally, currently pending commonly owned U.S. patent application Ser. Nos. 08/352,133 and 08/388,265 disclose digitizer coordinate input devices as set forth above in which the tablet driver, operating system, and application program work in conjunction with one another to process received stylus coordinate indicative data.
Coordinate input systems which have erasing capability are also well-known in the art. See, for example, U.S. Pat. Nos. 4,697,050; 5,272,470; 5,325,110; and 5,401,916.
U.S. Pat. No. 4,697,050 discloses a stylus for digitizing graphical data by way of a corresponding digitizing table. The stylus or pen is double ended, with one end functioning as a writing tip and the other end as an erasing tip. By outputting an erasing frequency, the digitizer pen of the '050 patent causes information to be erased. A switch for controlling the generation of a magnetic field indicative of frequency is actuated by way of, for example, a switch sensitive to pressure exerted by the stylus on a drawing table. Additionally, there appears to be no way for the system of the '050 patent to determine whether the erase end or the write end of the pen is adjacent the table upon pen entry into the sensing proximity of the table.
U.S. Pat. No. 5,325,110 discloses an eraser stylus for use on a graphical display screen. The stylus may be replaced with a mouse. The width of the erasing swath of the eraser icon in the graphics image environment is determined by the stylus position on the eraser icon, which is on the screen. For example, in one embodiment of the '110 patent, a plurality of distinct areas are provided on the display screen (e.g. CRT). When the stylus tip is placed in a first area, the stylus may be moved (while dragging along with it the second or eraser area) anywhere across the screen without altering or erasing the present graphical images. However, when the stylus is placed in the second or erasing area of the screen, erasure is performed of the graphical images on the screen located in the path taken by the stylus tip. The erasing width can be altered by placing the stylus in different areas of the second or erasing area of the screen. Additionally, a drop shadow image may be provided in the '110 patent so as to indicate to the user which mode (e.g. erase or non-erase) the system is in.
Unfortunately, the erasing aspects of the above-referenced prior art patents suffer from a number of problems. In order to analyze these problems, it is first necessary to briefly mention cursor and cursor shape functionality in commonly known applications. For example, in known application programs, "I-beam" cursor shapes are provided on the display screen in order to signal to the user that text is being edited or entered. On the other hand, "large +" cursor shapes are used in some application programs as a cursor shape to enter and edit particular cells where data is represented in arrays, such as in a spreadsheet. "Thin +" cursor shapes are often used in graphical or drawing applications. Additionally, "arrow shape" cursor shapes are often used on the display screen in many application programs for general navigation applications, such as pulling down menus and scrolling documents. Cursor shapes on the screen are changed in current systems by the application program first retrieving the cursor shape data, often by requesting a standard shape from the operating system by a call to "Get Cursor" or "Retrieve Cursor". The cursor shape is then set on the screen by passing the retrieved cursor shape data from the application program back to the operating system by a call to "Set Cursor".
The ability to erase text or graphical information being portrayed on the screen is not desireable in all circumstances. For example, while it may be useful to be able to erase text and other objects (e.g. drawings) on the display screen in certain environments, it may not be desireable to erase certain material in different environments. For example, it is sometimes undesirable to erase a character preceding an insertion point or a drawing object currently selected when the user is navigating on a different area of the screen. The above-referenced prior art patents which utilize erasing functionality do not take into consideration these problems. In other words, prior art eraser systems do not take into account the fact that it is often not desireable to erase particular data from the display screen. In view of this, it is apparent from the above that there exists a need in the art for a digitizer erasing system and method which, while being able to erase particular objects and text from the screen, is prohibited from erasing other specified data.
The above-identified prior art patents also suffer with respect to user feedback. It is desireable to let the user know, simply by viewing the cursor shape (where the user's focus typically is) being displayed on the screen, whether or not the system is in an erase mode or, for example, a write mode. While the '110 patent discussed above utilizes a shadow image to inform the user which mode the system is in, the drop shadow of the '110 patent does not adjust to different cursor shapes. The shadow image of the '110 patent is only associated with the erase area or tool on the screen, not with other usable cursor shapes and areas which may be utilized by the user in editing, navigating, etc. Thus, the user feedback is only given at the tool location; and not at the cursor itself. Because the user's attention is typically focused on the cursor, this is a problem associated with the '110 patent.
In view of the above, it is apparent that there exists a need in the art for a digitizer erasing system including a user feedback method and system applicable to and focused at a plurality of cursor shapes to be used on the screen, where the user is informed, simply by viewing the cursor shape being viewed, whether the cursor or system is in an "erase" mode or otherwise.
Furthermore, the above-described prior art erasing systems suffer from the apparent fact that the same method of erasing is employed no matter what the user is doing. In other words, erasing of information is carried out in the same manner whether the user is pulling down menus, scrolling a document, entering and editing cells, editing spreadsheets, entering and editing text, etc. This represents a problem in view of the fact that certain methods of erasure affect different areas of the system in different ways. For example, let us assume that erasing is being carried out in all cases by simulation of a "command X" keystroke. The use of this keystroke has different effects in some systems dependent upon whether it is carried out in a spreadsheet, a menu, or a text environment. For example, this keystroke will wipe out clipboard information in certain MS-WINDOWS.TM. applications, even if the clipboard is not being displayed. In view of this, it is not desirable to use the "command X" keystroke to erase in all circumstances although it will work fine in many situations. The above-referenced erasing systems do not take this into consideration.
It is apparent from the above that there exists a need in the art to customize the method of erasing (e.g. the keystroke or keystrokes utilized to carry out erasing) in response to the environment (e.g. cursor shape being used or window being used in PC-based applications) in which the user is erasing. Thus, the erasing of text in a document may be carried out by one keystroke function, and the erasing of spreadsheet data may be carried out by another so as to improve over the prior art.
It is a purpose of this invention to fulfill the above-described needs, as well as other needs in the art which will become more apparent to the skilled artisan once given the following disclosure.